diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
index eb24efea8f14..6f46e627aab3 100644
--- a/drivers/scsi/st.c
+++ b/drivers/scsi/st.c
@@ -2964,7 +2964,7 @@ static int st_int_ioctl(struct scsi_tape *STp, unsigned int cmd_in, unsigned lon
 			    !(STp->use_pf & PF_TESTED)) {
 				/* Try the other possible state of Page Format if not
 				   already tried */
-				STp->use_pf = !STp->use_pf | PF_TESTED;
+				STp->use_pf = (STp->use_pf ^ USE_PF) | PF_TESTED;
 				st_release_request(SRpnt);
 				SRpnt = NULL;
 				return st_int_ioctl(STp, cmd_in, arg);